Provides access to the underlying nsIFile object corresponding to a URL. The URL scheme need not be file:, since other local protocols may map URLs to files (e.g., resource:).
Get/Set nsIFile corresponding to this URL. The getter returns a reference to an immutable object. Callers must clone before attempting to modify the returned nsIFile object.
Note: This constraint might not be enforced at runtime, so beware! The setter clones the nsIFile object (allowing the caller to safely modify the nsIFile object after setting it on this interface).